Seven research projects are in progress: 1. The role of Na ion-K ion ATPase in sodium transport in the small intestine is examined in an in vivo model (canine ileal loops, superior mesenteric artery infusion of ouabain). 2. The effect of the hormone somatostatin on sugar and amino acid absorption is evaluated in the human jejunum. 3. Perfusion studies in the proximal small bowel in man are used to examine the secretory effect of VIP (vasoactive intestinal polypeptide), the agent that possibly causes the pancreatic cholera syndrome. 4. The mechanisms of rectal continence and the sphincter malfunction in some diarrhea patients with incontinence is studied by manometric and mechanical force registration techniques. 5. Calcium absorption is studied in patients with renal insufficiency. 6. The role of portal hypertension on water and electrolyte absorption is investigated in patients with cirrhosis of the liver. 7. Patients with intractable diarrhea are studied with a protocol that has been designed to test pathophysiological mechanisms of water and electrolyte movements in the intestine.